1. Field of the Invention
THIS INVENTION relates to measures for combating counterfeiting, particularly counterfeiting of banknotes and like documents, but also counterfeiting of other items such as packaging for perfumes, drugs, spirits, wine, CDs, CD ROM disks, records, tapes, etc., and the packaging therefor.
2. Description of the Related Art
There are many and various ways of making it difficult for counterfeiters to produce counterfeit banknotes which will escape detection by experts scrutinizing the counterfeit notes closely, but it is a fact well known to counterfeiters that the majority of people handling banknotes and other products do not scrutinize these carefully and, for the most part, do not have the expertise necessary to detect forgeries, even after such close scrutiny. Accordingly, there is a demand for some means which would allow ordinary individuals, without undue effort, to detect counterfeit notes reliably. Various proposals have been made to this end and, indeed, devices purporting to fulfil this requirement are available, for example devices which rely upon fluorescence under ultraviolet light, and devices in the form of marker pens which apply a fluid which can undergo a colour change, due to chemical reaction, but these known expedients are unreliable in that they may both indicate genuine notes as being counterfeit and may fail to detect counterfeits, particularly since counterfeiters have become aware of these expedients and select or treat the materials they use accordingly.
One difficulty with conventional security markings, for example, serial numbers or bar codes, is that the fact that they are security markings is plainly evident on even a casual inspection so that forgers will naturally exercise care to reproduce such markings accurately.
It is an object of the present invention to provide an anti-counterfeiting marking which can effectively be camouflaged and which yet will allow of verification automatically without requiring skill or the expenditure of undue time by the user.
According to a first aspect of the invention there is provided anti-counterfeiting marking for items such as banknotes and like documents, which marking is disguised as an incidental or artistic feature of overall marking on the banknotes or like documents, but is adapted to be read by a complementary reading device.
In preferred embodiments of the invention, said marking is a one, two or three-dimensional statistically fractal marking. This marking may be combined with, or incorporate, a regular or miniaturised routine bar bode providing details of the product.
Preferably, in this case, the marking is statistically fractal and is representative of an array of digits in which the value of each digit is represented by the fractal dimension, as herein defined, over a corresponding region, or set of regions of the area of a product, e.g. a banknote or like document such as a label bearing the marking.
Random scaling fractal fields look natural, because fractal geometry is based on fundamental characteristics of nature and possesses self-affinity. In particular, random scaling fractal signals are statistically self-affine, i.e. the statistics of the signals are invariant of scale.
In addition to the advantage of unobtrusiveness, the fractal code marking proposed in accordance with the preferred embodiment of the invention lends itself to the provision of redundancy of the coding information, so that, for example, a banknote which has become damaged or defaced can still have its code marking read to a high level of reliability.
According to a second aspect of the invention, there is provided an apparatus for reading an anti-counterfeiting marking according to the first aspect of the invention, including light sensing means for determining the relative density (darkness or lightness) of each elemental area in a set of elemental areas occupying predetermined positions within, and with respect to, a notional window in the area of such marking and means for deriving from the densities so determined a numerical value statistically representative of said set, said apparatus being adapted to conduct a scan of said window over the area of said marking and to determine such a value for each of a plurality of reference positions of such window within such scan, and means to determine from said values a corresponding indicator or string, such as a number or text, the apparatus further including means for displaying the last-noted number or text or for comparing it, for validation purposes with a predetermined string/indicator.
In one embodiment of the invention, said predetermined positions are successive positions in a linear series of such positions and the apparatus is adapted to scan said window along a line parallel with a notional line along which said predetermined positions are disposed.
By way of example, successive said reference positions of said window may, in this case, be such that the elemental area of the document scanned which is disposed in a said predetermined position in said window in one such reference position is the elemental area which was disposed in the succeeding said predetermined position in said series, in the preceding reference position in said scan, so that each said elemental area, in the course of such scanning, contributes to a succession of said values.
In a further development, the apparatus may be adapted to effect a raster scan of the coded area of the banknote or other document, with each line of the raster being treated as a respective linear scan.
Where, as is preferred, the coded area of the banknote or the like is statistically fractal, the apparatus is preferably arranged to calculate said values as at least approximately the fractal dimension, as defined in document D1, of the portion of the marking within said window.
The reader may be equipped to read other encoded information such as a routine bar code.
The fractal encoding/decoding system in accordance with the invention may utilise the techniques and principles disclosed in more detail in Blackledge J. M., Foxon B., and Mikhailov S., Fractal Dimension Segmentation, published by SERCentre, De Montfort University, Leicester (Research Monograph No. 12, September 1996) and in Image Processing: Mathematical Methods, Algorithms, and Applications (Ed. J. M. Blackledge) Oxford University Press, 1997, pp. 249-292. The last-noted document is herein referred to, for convenience, as document D1.
With the contemplated coding arrangement in accordance with the invention, key management is not necessary, provided that the fractal code marking is not recognised for what it is.
It is among the objects of the present invention to provide an anti-counterfeiting means which will provide reliable detection of counterfeit notes without requiring skill or the expenditure of undue time by the user.
According to a third aspect of the invention there is provided apparatus for use in detecting counterfeit items, for example for detecting counterfeit banknotes or the like documents, which carry code markings conforming to any of a large but limited number of combinations and/or permutations of such code markings provided on genuine items among a significantly larger number of possible combinations and/or permutations of such markings, the apparatus including means for reading such code markings, means for storing a record of valid marking combinations and/or permutations, and means for comparing the code markings read with said record to determine whether or not a particular code marking read is a valid one and to provide an audible or visible indication of the determination reached.
According to a fourth aspect of the invention, unconnected with anti-counterfeiting measures, (or at least not necessarily connected with such), there is provided a mask suitable for use in the production of a light-diffusing screen using a photopolymer, the mask comprising an opaque layer or coating having an array of light transmitting apertures or windows therein, and wherein said apertures or windows are of at least three different sizes and/or shapes.
According to a fifth aspect of the invention, there is provided a method of making a light-diffusing screen comprising superimposing a mask according to the last-noted aspect on a layer of a photopolymerisable material or a layer of otherwise photo-modifiable material and exposing said layer to light through said mask.
According to another aspect of the invention, therefore, there is provided anti-counterfeiting means for items, such as banknotes and like documents, comprising a coded array of markings readable by a complementary reading device.
According to a still further aspect of the invention there is provided an anti-counterfeiting or anti-copying means for media bearing sound or video recordings, computer data or the like such as, for example, compact discs (herein referred to as CDs) or tape cassettes or magnetic discs (diskettes) bearing sound recordings or computer software, in which the recording itself, or alternatively a decoding key or algorithm, is embodied in the recording, or alternatively, or additionally, in a visible or otherwise readable fractal marking on the recording medium itself.